1. Field of the Invention
The present invention relates to a switching control circuit preferably in the form of an IC for use in a switching power supply device and a switching power supply device including the switching control circuit.
2. Description of the Related Art
In switching power supply devices, a switching control IC includes a circuit for achieving various functions such as an output control function, an activation function, an overcurrent protection function, an overvoltage protection function, a waiting function, and a power factor improvement function. With the increase in the number of functions, the functionality of the switching control IC is increased. For example, upon detecting an overcurrent state, a switching control IC having an overcurrent protection (current control) function holds the non-operational state of a switching operation of a switching element (performs a latch method), or stops the switching operation of the switching element and automatically restarting the switching operation (performs a hiccup method). Accordingly, in accordance with the design of a switching power supply device, one of a switching control IC using a latch method and a switching control IC using a hiccup method is selected for use.
Paragraph [0014] of Japanese Unexamined Patent Application Publication No. 2008-206271 describes a switching control IC using both a latch method and a hiccup method for an overcurrent protection circuit. In the switching control IC using both methods, a single dedicated terminal for selecting one of these methods is provided, and one of these methods is selected in accordance with a signal input into the dedicated terminal or is selected by an external component/circuit.
When a switching control IC using a latch method and a switching control IC using a hiccup method are separately designed and manufactured for use in a switching power supply device having an overcurrent protection function, the number of types of switching control ICs is increased. Not only a manufacturing process but also the management of the ICs is therefore complicated. This leads to the increase in the unit cost of an IC.
For the switching control IC using both a latch method and a hiccup method disclosed in Japanese Unexamined Patent Application Publication No. 2008-206271, a dedicated terminal for selecting one of these methods is required. The number of terminals of the switching control IC is therefore increased. This inhibits the reduction in size of the switching control IC and increases the cost of the switching control IC. That is, the package and unit cost of the switching control IC are increased.
In response to a request for the reduction in the size and footprint of a switching control IC, a switching control IC having a small number of terminals is needed. Accordingly, it is impossible to provide the above-described dedicated terminal.